The present invention relates generally to clutch actuation systems for vehicles and, more particularly, to a friction-based clutch actuation system for a powertrain of a vehicle.
It is known to provide a clutch actuation system for a powertrain of a vehicle such as a motor vehicle. In the powertrain, the clutch actuation system may be used to shift gears in an automatic transmission. Typically, the clutch actuation system is of a hydraulic type. The hydraulic clutch actuation system has a plurality of input clutch plates connected to an input shaft and a plurality of output clutch plates connected to an output shaft and alternated between the input clutch plates. When the hydraulic clutch actuation system is not applied, these plates are free to rotate relative to each other. To apply the hydraulic clutch actuation assembly, a fluid actuating device such as a hydraulic piston is slidingly mounted for axial movement on an input clutch retainer connected to the input shaft. Fluid pressure between the input clutch retainer and the hydraulic piston causes the hydraulic piston to engage the input clutch plates with the output clutch plates. A return spring is disposed between the hydraulic piston and a retainer connected to the input shaft to bias or return the hydraulic piston to its non-displaced or non-applied position. However, in the automatic transmission, the hydraulic clutch actuation system requires high stroke (xcx9cmm) and high force (xcx9ckNs). This results in hydraulic pump losses, low robustness, poor efficiency, and a penalty in fuel economy.
Prior clutch actuation systems have explored the use of motors, electromagnets, and smart materials like magneto-rheological fluids. These systems, while they tend to eliminate the disadvantages of the hydraulic clutch actuation system, lead to other disadvantages. In addition, other clutch actuation systems have used piezoelectric and magneto-strictive materials and servo motors. While electric motors typically offer high stroke (xcx9cmm), they suffer from the disadvantage of low force (xcx9cNs). While piezoelectric and magnetostrictive actuators typically offer high force (xcx9ckNs), they suffer from the disadvantage of small stroke (xcx9cxcexcms).
As a result, it is desirable to provide a friction-based clutch actuation system that has easily controllable mechanisms. It is also desirable to provide a friction-based clutch actuation system that has quick response. It is further desirable to provide a friction-based clutch actuation system that has improved efficiency. It is still further desirable to provide a friction-based clutch actuation system that eliminates disadvantages of existing hydraulic clutch actuation systems. Therefore, there is a need in the art to provide a friction-based clutch actuation system that meets these desires.
It is, therefore, one object of the present invention to provide a friction-based clutch actuation system.
It is another object of the present invention to provide a friction-based clutch actuation system that splits stoke and force functions.
To achieve the foregoing objects, the present invention is a friction-based clutch actuation system including a rotatable input shaft, an output shaft, at least one input clutch plate operatively supported by the input shaft, and at least one output clutch plate operatively supported by the output shaft and moveable thereon. The friction-based clutch actuation system also includes at least one electric motor and at least one piezoelectric actuator operatively connected to the at least one electric motor. The friction-based clutch actuation system further includes a controller electrically connected to the at least one electric motor and the at least one piezoelectric actuator. The controller activates the at least one electric motor to move the at least one piezoelectric actuator relative to the at least one output clutch plate. The controller also activates the piezoelectric actuator to apply a force to the at least one output clutch plate to engage the at least one output clutch plate.
One advantage of the present invention is that a friction-based clutch actuation system is provided. Another advantage of the present invention is that the friction-based clutch actuation system uses piezoelectric actuators for force and direct current motors for stroke to split the force and stroke functions of the friction-based clutch actuation system. Yet another advantage of the present invention is that the friction-based clutch actuation system eliminates the hydraulic pump and hydraulic pump losses, thereby improving vehicle fuel economy. Still another advantage of the present invention is that the friction-based clutch actuation system eliminates drawbacks of existing hydraulic actuation like poor robustness, leading to better performance and quick response. A further advantage of the present invention is that the friction-based clutch actuation system has a simple construction. Yet a further advantage of the present invention is that the friction-based clutch actuation system has a direct interface with electronics, leading to easier and more precise control. Still a further advantage of the present invention is that the friction-based clutch actuation system has lower power consumption because very little power is required to maintain engagement. Another advantage of the present invention is that the friction-based clutch actuation system may incorporate a dual stage using a cam such that a first stage provides a long stroke with relatively low force and the second stage provides a high force but with a short stroke. Yet another advantage of the present invention is that the friction-based clutch actuation system can be used for rotating and non-rotating clutches.
Other objects, features, and advantages of the present invention will be readily appreciated, as the same becomes better understood, after reading the subsequent description taken in conjunction with the accompanying drawings.